1. Field of the Invention
The present invention relates to a semiconductor laser device and a method of manufacturing the same, and more particularly, it relates to a semiconductor laser device integrating a plurality of semiconductor laser elements and a method of manufacturing the same.
2. Description of the Background Art
A semiconductor laser element (infrared semiconductor laser element) emitting infrared light having a wavelength of about 780 nm is employed as a light source for a CD (compact disk)/CD-R (compact disk-recordable) drive in general. A semiconductor laser element (red semiconductor laser element) emitting red light having a wavelength of about 650 nm is employed as a light source for a DVD (digital versatile disc) drive.
On the other hand, a DVD allowing writing and reading by employing blue-violet light having a wavelength of about 405 nm has recently been developed. For writing and reading of such a DVD, a next generation DVD drive employing a semiconductor laser element (blue-violet semiconductor laser element) emitting blue-violet light having a wavelength of about 405 nm has also simultaneously been developed. This DVD drive requires compatibility for conventional CD/CD-R and DVD.
In this case, the compatibility for the conventional CD/CD-R and DVD is attained by a method of providing a plurality of optical pickups emitting infrared light, red light and blue-violet light respectively in a DVD drive or a method of individually providing an infrared semiconductor laser element, a red semiconductor laser element and a blue-violet semiconductor laser element in one optical pickup. However, these methods cause increase of the number of components, and hence downsizing, simplified configuration or price-reduction of the optical pickup system is disadvantageously difficult.
In order to suppress the increase of the number of components, a semiconductor laser element in which an infrared semiconductor laser element (laser having a wavelength of about 780 nm) and a red semiconductor laser element (laser having a wavelength of about 650 nm) formed on a gallium arsenide substrate are integrated in one chip has been put into practice in general. In the integrated semiconductor laser element in the one chip, the light emission positions of the respective wavelength semiconductor laser elements are accurately formed.
The blue-violet semiconductor laser element not formed on the gallium arsenide substrate, on the other hand, it is very difficult to integrate the blue-violet semiconductor laser element together with the infrared semiconductor laser element and the red semiconductor laser element in one chip. The light emission positions of the respective wavelength semiconductor laser elements must be arranged as close as possible in order to reduce loss or aberration to laser beams emitted from the respective wavelength semiconductor laser elements.
A semiconductor laser device having a structure, in which semiconductor laser elements are individually formed on different growth substrates and thereafter are bonded to each other such that emission layers of the semiconductor laser elements are opposed to each other, is proposed in general, as disclosed in Japanese Patent Laying-Open Nos. 2005-209950 and 2007-488100, for example.
The aforementioned Japanese Patent Laying-Open No. 2005-209950 discloses an integrated semiconductor light-emitting device having a structure in which emission layers (semiconductor element layers) of a red semiconductor laser element and a blue semiconductor laser element are bonded to be opposed to each other. In the integrated semiconductor light-emitting device described in Japanese Patent Laying-Open No. 2005-209950, the emission layer of the blue semiconductor laser element is fitted into a recess portion (groove) formed on a prescribed region of the emission layer of the red semiconductor laser element and reaching the growth substrate through a bonding layer so that p-side semiconductor layers of the red semiconductor laser element and the blue semiconductor laser element are electrically connected to each other. In particular, the bonding layer are so formed as to cover the overall surface region of the semiconductor laser element including portions where the growth substrate and an n-side semiconductor layer are exposed, and a p-side electrode is mounted on a first end of the bonding layer, so that the integrated semiconductor light-emitting device can be employed in a common anode type (p-side common electrode).
In the integrated semiconductor light-emitting device described in Japanese Patent Laying-Open No. 2005-209950, insulating layers are provided between the growth substrate and the n-side semiconductor layer of the red semiconductor laser element and the bonding layer so as to cause no electrical short circuit between the growth substrate as a cathode side (n-side) and the n-side semiconductor layer of the red semiconductor laser element and a region of the bonding layer (p-side). Additionally, insulating layers are provided between the growth substrate and the n-side semiconductor layer of the blue semiconductor laser element and the bonding layer so as to cause no electrical short circuit between the growth substrate as the cathode side (n-side) and the n-side semiconductor layer of the blue semiconductor laser element and the region of the bonding layer (p-side).
The aforementioned Japanese Patent Laying-Open No. 2007-488100 discloses a semiconductor laser having structure in which a blue-violet semiconductor laser element (first light-emitting element) and a semiconductor laser element (second light-emitting element) integrally formed with a red semiconductor laser element and an infrared semiconductor laser element are bonded to a support substrate in a state where the emission layers (semiconductor element layers) of the first light-emitting element and the second light-emitting element are opposed and bonded to each other. In the semiconductor laser described in Japanese Patent Laying-Open No. 2007-488100, p-side semiconductor layers of the first light-emitting element and the second light-emitting element are arranged so as to be opposed to each other and insulating layers are provided between the opposed p-side semiconductor layers, whereby the p-side semiconductor layers of the respective light-emitting elements are electrically insulated from each other. Therefore, electrodes connected to the p-side semiconductor layers of the respective light-emitting elements are formed on the support substrate and an electrode connected to the n-side semiconductor layer of the first light-emitting element is also connected to the support substrate.
In the integrated semiconductor light-emitting device disclosed in Japanese Patent Laying-Open No. 2005-209950, however, the p-side semiconductor layers of the red semiconductor laser element and the blue semiconductor laser element are electrically connected to each other through the bonding layer, while the insulating layers for preventing a short circuit must be formed between the portions of the growth substrates and the n-side semiconductor of the respective semiconductor laser elements layers are exposed and the bonding layer as an anode side (p-side) respectively, and hence an inner structure of the semiconductor laser element is disadvantageously complicated.
In the semiconductor laser disclosed in Japanese Patent Laying-Open No. 2007-488100, the insulating layers must formed in order to electrically isolate the p-side semiconductor layers of the first and second light-emitting elements while the p-side semiconductor layers of the respective light-emitting elements are arranged to be close to each other. Thus, the inner structure of the semiconductor element is disadvantageously complicated.